More Patterns of

Inheritance

Incomplete Dominance

• A cross where neither allele is dominant over the other.

• The traits appear to be blended together.

• Ex. Snapdragon flowers• RR=Red• WW=white• RW=pink

The Cream Dilution GeneIs white when homozygous.

What will it do to horses?

Bay is brown with black.

CREAM and BROWN

produce New color: BUCKSKIN

brown with black.

What Pattern of Color Inheritance Does this show?

Cream dilutes red-brownTo make….

PALOMINO, a golden color.

IncompleteIncompleteDominanceDominance

Codominance• A cross where both alleles are equally expressed.

• Ex. Horse Coats– CBCB=Brown coat– CWCW=White coat– CBCW=Roan coat: has both brown and white hairs.

Co-dominance

Andalusian Chickens

• Black feathers and white feathers are co-dominant. • Cross FB FB and FW FW and what will be produced?

Andalusian Chickens

Q: Cross FB FB and FW FW and what will be produced?A: A Steel Blue Chicken FB FW

Do this:

1.Cross a heterozygous red

rose with a homozygous

recessive yellow rose. Red

is the dominant allele.

What are the possible

colors of offspring?

X

What will the offspring look like?

2. A farmer is planning to

mate a bull and cow. The

male has a roan coat (brown

and white hairs) and the

female has a white coat

(white hairs). What might

their calves look like?

X

What will the offspring look like?

3. Your parents have decided to plant some snapdragons and want to know why there are three colors – red, pink and white. You volunteer to explain it to them by showing them the cross of 2 hybrid pink snap dragons – what are the possible offspring?

4. You and your partner carry sickle cell trait.What are your chances of having a baby with

sickle cell anemia? Use RR for normal blood. RS for carriers and SS

for sickle cell anemia.

Normal

Carrier

Sickle Cell Anemia

5. Two heterozygous parents with free earlobes have 4 children predict the genotypes and phenotypes for the children’s ears.

F = free ear lobesff = attached ear lobes

XHybrid

Hybrid

XHybrid

Hybrid

Warm-Up• No blurting – give everyone a chance

• Decide if the pictures are examples of:– Simple dominance– Incomplete dominance– Codominance

Andalusian Chickens

Warm-Up• Complete this problem in your journal:–If a man an a woman are having a baby, what are the chances the baby will be a boy? Use a Punnett Square to justify your answer. Hint: Think about which chromosomes a male has and which ones a female has

Blood Types are an example of co-dominance

Human Blood Types

Phenotype:The protein

Genotype:The genes

A IAIA or IAi

B IBIB or IBi

AB IAIB

O ii

Blood type rules

• A is dominant over O• B is dominat over O• O is recessive to A and B• A and B are co-dominant to each other.

• Genes that are located on the X sex chromosomes.

• Males will have one copy of the gene. Normal male- XB YAffected Male- Xb Y• Females Will have 2 copies of the gene:

Normal Female – XB XB

“Carrier” Female – XB Xb Affected Female – Xb Xb

X-Linked Genes

Gender Determination• (Very few genes are found on the Y Chromosome)

• Only females can be carriers for sex-linked disorders on the X.

XY

Carrier – a person who transports the recessive allele but does not show the recessive trait. *Are they heterozygous or homozygous?*

X Chromosome

• Recessive genes found there:– Colorblindness Xc

– Baldness Xb

– Hemophilia - bleeding disorder where blood won’t clot. Xh

A male with the XbY will have the recessive trait for baldness.

Polygenic• A trait that is produced (controlled) by two or more genes

Eye Color Example

• Controlled by at least three genes.• Act together to produce your eye color

Lethal Genes

• Any genetic trait that causes death.Examples:Hemophilia- bleed to deathHuntington’s disease- brain shrinks

Lethal Genes

Hemophilia (lethal and sex-linked) bleed to deathXhY

Lethal Genes

Huntington’s disease- brain shrinks